The invention relates to a data transmission system using 50 Hz or 60 Hz domestic alternating mains supply as a transmission path.
It has already been suggested that existing electrical installations in residential premises should be used as transmission paths for control commands (Markt und Technik, issue No. 22, May 30, 1980, page 85). In the proposed transmission system a control station is connected to the lighting mains. With the aid of the input keyboard arranged in the control station switching and control commands are passed on via the control station to devices which are connected via a decoder device to the alternating mains supply. Furthermore, it has also already been suggested that the existing electrical installations of residential premises should be used as a transmission path for intercommunication systems. The signal is frequency modulated, passed to the 50 Hz lighting mains and reproduced at the receiving location, after demodulation, through a loudspeaker. The combined speech and receiving location of these intercommunication systems is then connected to a socket of the lighting mains. These devices are permitted by the telecommunications authorities in some countries.
The proposed transmission system has the disadvantage that a fixed electrical connection always has to be present in the system if domestic appliances are to be controlled or monitored, if data is to be fed in or scanned, or if speech is to be transmitted.